1. Field of the Invention
The invention provides a process for efficient and reliable preparation of organic peroxides, preferably dialkyl peroxides, peroxycarboxylic acids, peroxycarboxylic esters, diacyl peroxides, peroxycarbonate esters, peroxydicarbonates, ketone peroxides and perketals with the aid of at least one static micromixer and an apparatus for performing the process.
2. Description of Related Art
Organic peroxides are very reactive chemical substances. Since they decompose readily to extremely active free radicals and oxygen, they are used as initiators in the plastics and rubber industry. Fields of use of the organic peroxides are the polymerization of monomers for plastics production, the crosslinking and the modification of polymers, and the curing of polyester resins. In addition, organic peroxides are used as oxidizing agents in medical preparations and for complicated chemical syntheses.
A significant feature of organic peroxides is the SADT (Self-Accelerating Decomposition Temperature). It is the lowest temperature at which self-accelerating decomposition in the transport packaging can occur. A dangerous self-accelerating decomposition reaction, and under unfavorable circumstances explosion or fire, can be caused by thermal decomposition at or above the temperature specified. Contact with incompatible substances and also increased mechanical stress can cause decomposition at or below the SADT.
Organic peroxides are now prepared by continuous or batchwise processes (Chem. Ztg. 98 (tg. 12), 583 (1974), W. Mayr. Ullmann's encyclopedia of industrial chemistry, 6th edition, vol.25, 463 (2002)), DE 698 12 430 T2, DE 699 04 337 T2 or else U.S. Pat. No. 6,268,523. A typical example is the preparation of tert-butyl peroxy-2-ethylhexanoate. This organic peroxide is prepared from tert-butyl hydroperoxide and 2-ethylhexanoyl chloride at a temperature below 35° C. (=SADT) and an average residence time of up to 2 hours in a 500 kg reaction batch in a stirred tank. Specifically, the following illustrative reaction schemes are relevant for the preparation of individual peroxide classes:
Acid chlorides and hydrogen peroxide form diacyl peroxides:

Chloroformates and hydrogen peroxide form peroxydicarbonates:

Acid chlorides and organic hydroperoxides form peroxyesters:

Chloroformates and organic hydroperoxides form percarbonate esters:
where R is any organic radical.
A significant parameter in the preparation of organic peroxides is optimal temperature control while maintaining the required residence time for the reaction. Experience has shown that the required reaction temperature is in the range of the aforementioned SADT, such that localized exceedance of the reaction temperature in the reactor, which can lead to uncontrollable decomposition of the reaction mixture or of the reaction products, must be prevented. This likewise leads to long reaction times. In the known preparation processes, large amounts of a few hundred liters of the very reactive and explosive reaction mixture accordingly have to be maintained with maximum turbulence in vessels or other reaction systems. This procedure entails a not inconsiderable level of special safety devices, for example in the temperature and turbulence monitoring sector.
Moreover, to increase the reaction safety, the reaction has to be performed at high dilution. This gives rise to a significant additional employment of diluent and a corresponding requirement for downstream removal, purification and workup processes. In addition, this slows the reaction and also the overall preparation process. Furthermore, virtually all preparation methods are biphasic reactions, since the reactants are not entirely miscible with one another. In order to achieve a sufficient reaction rate, intensive finely dispersed mixing of the two phases is necessary. This can be achieved only insufficiently, for example, in a conventional stirred tank reactor. Preparation in other static mixers or tubular reactors is inadvisable, even with incorporation of pressure release devices, for reasons of inhibition of the explosive organic peroxides.
DE 69618646 T2 discloses continuous and batchwise processes for preparing acyl peroxides. In these processes, vigorous stirring of the reactants by means of jet mixers, static mixers or else ultrasound mixers is intended to avoid problems with the stability of the reaction mixtures.
In the continuous processes, yields up to a maximum of 95.5% can be achieved, while the advantage is at shorter reaction times in the batchwise processes, but this is at the expense of the product yield.
Accordingly, no process which enables the preparation of organic peroxides without the above-described disadvantages, i.e. safe and rapid preparation in a high yield, is known in the prior art.